[wiltw]

I basically agree with you from my experience, but since different makes of cameras exposure systems have different parameters in their design it's quite possible to to have some small deviation in their responses when pointed at a Grey Card, I have noticed this myself in my cameras, but I don't find this in practice significant because in isolation each camera gives me correct exposure, and comparing light meter and thermometer readings I find is a very quick way to drive yourself crazy

And many of us know, from the routine use of EI 40 to expose Velvia which was rated ISO 50, that even the ISO ratings of film are rather arbitrary! So why would we be surprised to see some variability in ISO sensitivity within digital cameras, too?!

This brings us back to why I originally objected to your commentary in post 23, "so I.S.O 100 on a digital camera isn't the same as 100 I.S.O on a hand held separate light meter and film which is why the readings don't agree".

My digital camera meter matches my traditional handheld ('for film') meter! And my film camera meters don't all agree with each other, so they provide a shakey reference standard by which to judge digital camera meters, and film itself is not necessarily a perfect standard either, so film is an imperfect standard to compare against digital sensor sensitivity!